Conventionally, a high-pressure pump has been known, which is mounted on a vehicle and pressurizes and supplies a fuel to an internal combustion engine. The high-pressure pump disclosed in Patent Literature 1 includes a bottomed cylindrical cylinder, a plunger, and a coil spring. The plunger is disposed to reciprocate inside the cylinder, and defines a pressurizing chamber between an outer wall on one end of the plunger and an inner wall of the cylinder. The coil spring is provided radially outward of another end of the plunger and is capable of urging the other end of the plunger away from the pressurizing chamber and pressing the other end against a cam of a driven shaft of the internal combustion engine.
In the high-pressure pump of Patent Literature 1, gaps are provided between a retainer locking an end portion of the coil spring and the other end of the plunger and between a tappet provided between the retainer and the cam and the other end of the plunger. The gaps prevent radial force from acting on the plunger from the coil spring when the plunger reciprocates. As a result, a surface pressure of a sliding interface between the outer wall of the plunger and the inner wall of the cylinder is reduced, thereby reducing load acting on the plunger.
However, in the high-pressure pump of Patent Literature 1, when the plunger reciprocates, only a specific portion of the sliding interface between the plunger and the cylinder may slide. In that case, an oil film breakage occurs at the specific portion, which may cause uneven wear and burnout of the plunger and the cylinder.